Presumably, they sorta mediate interplanetary disputes, like between the Trade Guild and the Government of a planet, say, Naboo. Some sort of accord reached when a committee weighs both sides of the issue, and reaches a common middle ground. I suppose, they could also mediate in those cases when there are two sapient species on the same planet, with two rival governments, to reach an accord. Note: none of that actually happens. Everyone always try’s to play the system for their own benefit, or ignores it completely. Possibly because the arena is so distant, and so diverse, it just won’t work.